Ammonia is a colorless, pungent gas, NH3, highly soluble in water. A saturated aqueous (water) solution of ammonia contains 45 percent ammonia by weight at 0° C (32° F) and 30 percent at ordinary room temperatures. On solution in water, ammonia becomes ammonium hydroxide, NH4OH, which is strongly basic and similar in chemical behavior to the hydroxides of the alkali metals.
Ammonium carbonate, (NH3)2CO3·H2O, is a colorless-to-white crystalline solid commonly known as smelling salts; in water solution it is sometimes called aromatic spirits of ammonia.
Ammonia was known to the ancients, who derived both the name and the substance from sal ammoniac, which was produced at the Temple of Jupiter Ammon in Libya by the distillation of camel dung. During the Middle Ages in Europe ammonia was obtained by heating the horns and hoofs of oxen and was called spirits of hartshorn. Free ammonia was obtained by the German alchemist Basil Valentine; its composition was determined by the French chemist Comte Claude Berthollet about 1777.